macos: remove the ability to bind fn/globe

This was recently introduced a few days ago. Unfortunately, this doesn't
work as expected. The "function" modifier is not actually the fn key
but used by macOS to represent a variety of "functional" key presses.
This breaks other bindings such as #2411.

I can't find a source on the internet that reliably tells me how we
can detect fn key presses, but I do find a number of sources that tell
us we can't.

macos/Sources/App/macOS/AppDelegate.swift

@@ -354,11 +354,6 @@ class AppDelegate: NSObject,
             return
         }
 
-        if (equiv.modifiers.contains(.function)) {
-            // NSMenuItem key equivalent cannot contain function modifiers.
-            return
-        }
-
         menu.keyEquivalent = equiv.key
         menu.keyEquivalentModifierMask = equiv.modifiers
     }